Solar radiation travels through the earth's atmosphere and warms the planet's surface. greenhouse gases like carbon dioxide in the earth's atmosphere reabsorb the heat and warm the planet. the amounts of greenhouse gases have been increasing over the past century, causing the earth's surface temperature to increase. this gradual temperature change is thought to have many negative environmental consequences. which of these might be a positive effect of the increase in carbon dioxide levels? a) rise in sea levels b) decrease in plant growth c) increase in plant growth d) increased melting of ice caps